1. Field of the Invention
The present invention relates to a process for removing NO.sub.x from a gas under cryogenic conditions.
2. State of the Art
There are many ways to remove nitrogen oxides from gas streams. For example, U.S. Pat. No. 4,564,510 describes the removal of NO.sub.x from waste gases by absorption as a liquid. U.S. Pat. No. 4,656,014 discloses the removal of NO.sub.x from waste gas by catalytic reduction in the presence of unsaturated hydrocarbons at 120.degree. C.-180.degree. C. Japanese patent No. 52/85,967 describes a process for removing nitric oxide from waste gases by contacting the gas at temperatures of 300.degree. C.-1000.degree. C. with an aliphatic hydrocarbon in the presence of oxygen. In cryogenic gas separation systems, nitric oxide (NO) and nitrogen dioxide (NO.sub.2) are troublesome but, because of the low temperatures, the problems of NO.sub.x removal are not necessarily the same as at ambient or higher temperatures and one could not predict the chemical and physical behavior of various materials, particularly potential reactants, reaction promoters or catalysts.